Manufacture of viscose silk



Patented June 12, 1923.,

EMILE BRONNIERT, OF MULHOUSE, FRANCE.

MANUFACTURE OF VISCOSE SILK.

N0 Drawing;

To all whom it may concern:

Be it known that I, EMILE BRUNNERT, a citizen of the Republic of France, and resident of Mulhouse, France, haveinvented certain new and useful Improvements in the Manufacture of Viscose Silk; and I do hereby declare the following to be a full, clear, and exact description of the invention.

The present invention relates to an improvement of the process for the direct manufacture of the finest viscose silk by using baths containing a mixture of sulphuric acid and ammonium sulphate, such as disclosed in my U. S. Patent No. 1,419,714 of June 13, 1922.

This patent relates to the use of a spinning bath containing sulphate of ammonium as well as sulphuric acid for making very fine viscose silk thread fibres like those disclosed in my U. S. Patent No. 1,393,198, of Oct. 11, 1921, and comprises pre-determining the minimum limit of the concentration of acid in the following manner:

Assume the concentration of acid to be expressed in grams per liter and the diameter of the thread or fibre in denier's; also assume that the minimum concentration C of acid for a given denier D has been ascertained, then the approximate minimum concentration C for any other or desired denier D will be represented by the formula acid; or in lieu of a bath containing sulphuric acid alone.

In employing such solutions of ammonium sulphate not only the free sulphuric acid,

I but also the sulphuric acid contained in the ammonium sulphate itself must be considered, and it was found that two parts of sulphate of ammonia must be reckoned for one part of free sulphuric acid in the -for-. mula.

This enables fine spinning from any spinning apertures of the size customarily used, as described in my aforesaid Patent No. 1,393,198, and enables the calculation of the minimum concentration of sulphuric acid to be determined for any denier number from Application filed November 17, 1921.

Serial No. 515,988.

the concentrationfound to be good for any other denier number.

The present invention results in a cheapening of the cost of carrying out the process, on account of using a smaller quantity of the necessary ammonium sulphate.

Furthermore, the new proportions of the bath are strikingly adapted for an economic regeneration of the baths weakened during spinning, as described in my U. S. Patent 1,376,671 of September 7, 1920.

In the spinning of viscose in acidulated ammonium sulphate baths a-certain amount of sodium sulphate is of course formed, the smaller part of which remains in the spinning bath and the greater part is carried away with the fibre in and on which it is formed.

By systematically rinsing or scouring the fibres with dilute sulphuric acid and adding the rinsing solution to the" spinning bath after concentration by evaporation, a condition of equilibrium in salts is easily attained, and which has been found to be very advantageous.

The necessary minimum concentration of the acid or of the ammonium salt component has to be adjusted for each titre.

In spinning fibres of two deniers, for example, a bath of the following composition is gradually reached, which by the constant addition of only a little ammonium salt and the necessary quantity of sulphuric acid, whichis supplied with the salt and as concentrated rinsing solution above referred to,

it is easy tokeep the bath as constant as necessary for good spinning. The product will dye uniformly, and is of uniform physical characteristics.

The composition gradually reached is- Grams.

Sulphuric aci d 200 Ammonium sulphate 200 Sodium sulphate 300 Obviously the proportions of the two salts arenot rigidly fixed; for example, a certain amount of magnesium sulphate may also be added, provided the concentration of acid is adjusted to the degree of fineness required.

The threads spun from such a bath, containing not only sulphuric acid and ammonium sulphate but also the above mentioned sodiumsrilphate no longer have the characteristic round cross section of threads spun in baths containing only sulphuric acid and ammonium sulphate. Their cross-sec tion is changed to the well known irregular star-like or ribbon-like cross section with serrated or indented contours.

Fibres spun in such baths possess the property of. shrinking very little when drying, a particularly valuable property in the wholesale production of loosefibres, as the troublesome drying under tension is elimvinated.

I claim 1. Process of manufacturing threads of any deniers below six deniers from raw viscose, which comprises forcing viscose through openings of a vdiameter considerably larger than the diameter of the thread to be spun in the case of viscose of normal fluidity, into a bath containing sulphuric acid, ammonium sulphate and sodium sulphate, the minimum concentration of the acid component of which bath is inversely as furnished by a bath containing 200 grams of sulphuric acid, 200 grams of ammonium sulphate and 300 grams of sodium sulphate. In testimony that I claim the foregoing as my invention, I have, signed my name EMILE BRONNERT. 

